package InvertedIndex;

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * src: hadoop-0.20.2.1U11\ src\ core\ org\ apache\ hadoop\ util\LineReader.java 
 */

import java.io.IOException;
import java.io.InputStream;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Text;

/**
 * A class that provides a line reader from an input stream.
 */
public class NLineReader {
    private static final int DEFAULT_BUFFER_SIZE = 64 * 1024;
    private int bufferSize = DEFAULT_BUFFER_SIZE;
    private InputStream in;
    private byte[] buffer;
    // the number of bytes of real data in the buffer
    private int bufferLength = 0;
    // the current position in the buffer
    private int bufferPosn = 0;

    private static final byte CR = '\r';
    private static final byte LF = '\n';
    // The line delimiter
    private final byte[] recordDelimiterBytes;

    /**
     * Create a line reader that reads from the given stream using the
     * default buffer-size (64k).
     *
     * @param in The input stream
     * @throws IOException
     */
    public NLineReader(InputStream in) {
        this(in, DEFAULT_BUFFER_SIZE);
    }

    /**
     * Create a line reader that reads from the given stream using the
     * given buffer-size.
     *
     * @param in         The input stream
     * @param bufferSize Size of the read buffer
     * @throws IOException
     */
    public NLineReader(InputStream in, int bufferSize) {
        this.in = in;
        this.bufferSize = bufferSize;
        this.buffer = new byte[this.bufferSize];
        this.recordDelimiterBytes = null;
    }

    /**
     * Create a line reader that reads from the given stream using the
     * <code>io.file.buffer.size</code> specified in the given
     * <code>Configuration</code>.
     *
     * @param in   input stream
     * @param conf configuration
     * @throws IOException
     */
    public NLineReader(InputStream in, Configuration conf) throws IOException {
        this(in, conf.getInt("io.file.buffer.size", DEFAULT_BUFFER_SIZE));
    }

    /**
     * Create a line reader that reads from the given stream using the
     * default buffer-size, and using a custom delimiter of array of
     * bytes.
     *
     * @param in                   The input stream
     * @param recordDelimiterBytes The delimiter
     */
    public NLineReader(InputStream in, byte[] recordDelimiterBytes) {
        this.in = in;
        this.bufferSize = DEFAULT_BUFFER_SIZE;
        this.buffer = new byte[this.bufferSize];
        this.recordDelimiterBytes = recordDelimiterBytes;
    }

    /**
     * Create a line reader that reads from the given stream using the
     * given buffer-size, and using a custom delimiter of array of
     * bytes.
     *
     * @param in                   The input stream
     * @param bufferSize           Size of the read buffer
     * @param recordDelimiterBytes The delimiter
     * @throws IOException
     */
    public NLineReader(InputStream in, int bufferSize,
                       byte[] recordDelimiterBytes) {
        this.in = in;
        this.bufferSize = bufferSize;
        this.buffer = new byte[this.bufferSize];
        this.recordDelimiterBytes = recordDelimiterBytes;
    }

    /**
     * Create a line reader that reads from the given stream using the
     * <code>io.file.buffer.size</code> specified in the given
     * <code>Configuration</code>, and using a custom delimiter of array of
     * bytes.
     *
     * @param in                   input stream
     * @param conf                 configuration
     * @param recordDelimiterBytes The delimiter
     * @throws IOException
     */
    public NLineReader(InputStream in, Configuration conf,
                       byte[] recordDelimiterBytes) throws IOException {
        this.in = in;
        this.bufferSize = conf.getInt("io.file.buffer.size", DEFAULT_BUFFER_SIZE);
        this.buffer = new byte[this.bufferSize];
        this.recordDelimiterBytes = recordDelimiterBytes;
    }

    /**
     * Close the underlying stream.
     *
     * @throws IOException
     */
    public void close() throws IOException {
        in.close();
    }

    /**
     * Read one line from the InputStream into the given Text.
     *
     * @param str               the object to store the given line (without newline)
     * @param maxLineLength     the maximum number of bytes to store into str;
     * @param maxBytesToConsume the maximum number of bytes to consume
     *                          in this call.  This is only a hint, because if the line cross
     *                          this threshold, we allow it to happen.  It can overshoot
     *                          potentially by as much as one buffer length.
     */
    public int readLine(Text str, int maxLineLength,
                        int maxBytesToConsume) throws IOException {
        if (this.recordDelimiterBytes != null) {
            return readCustomLine(str, maxLineLength, maxBytesToConsume);
        } else {
            return readDefaultLine(str, maxLineLength, maxBytesToConsume);
        }
    }

    /**
     * Read one line from the InputStream into the given Text.  A line
     * can be terminated by one of the following: '\n' (LF) , '\r' (CR),
     * or '\r\n' (CR+LF).  EOF also terminates an otherwise unterminated
     * line.
     *
     * @param str               the object to store the given line (without newline)
     * @param maxLineLength     the maximum number of bytes to store into str;
     *                          the rest of the line is silently discarded.
     * @param maxBytesToConsume the maximum number of bytes to consume
     *                          in this call.  This is only a hint, because if the line cross
     *                          this threshold, we allow it to happen.  It can overshoot
     *                          potentially by as much as one buffer length.
     * @return the number of bytes read including the (longest) newline
     * found.
     * @throws IOException if the underlying stream throws
     */
    public int readDefaultLine(Text str, int maxLineLength,
                               int maxBytesToConsume) throws IOException {
    /* We're reading data from in, but the head of the stream may be
     * already buffered in buffer, so we have several cases:
     * 1. No newline characters are in the buffer, so we need to copy
     *    everything and read another buffer from the stream.
     * 2. An unambiguously terminated line is in buffer, so we just
     *    copy to str.
     * 3. Ambiguously terminated line is in buffer, i.e. buffer ends
     *    in CR.  In this case we copy everything up to CR to str, but
     *    we also need to see what follows CR: if it's LF, then we
     *    need consume LF as well, so next call to readLine will read
     *    from after that.
     * We use a flag prevCharCR to signal if previous character was CR
     * and, if it happens to be at the end of the buffer, delay
     * consuming it until we have a chance to look at the char that
     * follows.
     */
        str.clear();
        int txtLength = 0; //tracks str.getLength(), as an optimization
        int newlineLength = 0; //length of terminating newline
        //boolean prevCharCR = false; //true of prev char was CR
        long bytesConsumed = 0;
        do {
            int startPosn = bufferPosn; //starting from where we left off the last time
            if (bufferPosn >= bufferLength) {
                startPosn = bufferPosn = 0;
                //if (prevCharCR)
                //  ++bytesConsumed; //account for CR from previous read
                bufferLength = in.read(buffer);
                if (bufferLength <= 0)
                    break; // EOF
            }
            for (; bufferPosn < bufferLength; ++bufferPosn) { //search for newline
                if (buffer[bufferPosn] == LF) {
                    newlineLength = 1;
                    ++bufferPosn; // at next invocation proceed from following byte
                    break;
                }
                //if (prevCharCR) { //CR + notLF, we are at notLF
                //newlineLength = 0;
                //break;
                //}
                //prevCharCR = (buffer[bufferPosn] == CR);
            }
            int readLength = bufferPosn - startPosn;
            //if (prevCharCR && newlineLength == 0)
            // --readLength; //CR at the end of the buffer
            bytesConsumed += readLength;
            int appendLength = readLength - newlineLength;
            if (appendLength > maxLineLength - txtLength) {
                appendLength = maxLineLength - txtLength;
            }
            if (appendLength > 0) {
                str.append(buffer, startPosn, appendLength);
                txtLength += appendLength;
            }
        } while (newlineLength == 0 && bytesConsumed < maxBytesToConsume);
        //System.err.println(str);
        //System.err.println(bytesConsumed);
        if (bytesConsumed > (long) Integer.MAX_VALUE)
            throw new IOException("Too many bytes before newline: " + bytesConsumed);
        return (int) bytesConsumed;
    }

    /**
     * Read a line terminated by a custom delimiter.
     */
    private int readCustomLine(Text str, int maxLineLength, int maxBytesToConsume)
            throws IOException {
        str.clear();
        int txtLength = 0; // tracks str.getLength(), as an optimization
        long bytesConsumed = 0;
        int delPosn = 0;
        do {
            int startPosn = bufferPosn; // starting from where we left off the last
            // time
            if (bufferPosn >= bufferLength) {
                startPosn = bufferPosn = 0;
                bufferLength = in.read(buffer);
                if (bufferLength <= 0)
                    break; // EOF
            }
            for (; bufferPosn < bufferLength; ++bufferPosn) {
                if (buffer[bufferPosn] == recordDelimiterBytes[delPosn]) {
                    delPosn++;
                    if (delPosn >= recordDelimiterBytes.length) {
                        bufferPosn++;
                        break;
                    }
                } else {
                    delPosn = 0;
                }
            }
            int readLength = bufferPosn - startPosn;
            bytesConsumed += readLength;
            int appendLength = readLength - delPosn;
            if (appendLength > maxLineLength - txtLength) {
                appendLength = maxLineLength - txtLength;
            }
            if (appendLength > 0) {
                str.append(buffer, startPosn, appendLength);
                txtLength += appendLength;
            }
        } while (delPosn < recordDelimiterBytes.length
                && bytesConsumed < maxBytesToConsume);
        if (bytesConsumed > (long) Integer.MAX_VALUE)
            throw new IOException("Too many bytes before delimiter: " + bytesConsumed);
        return (int) bytesConsumed;
    }

    /**
     * Read from the InputStream into the given Text.
     *
     * @param str           the object to store the given line
     * @param maxLineLength the maximum number of bytes to store into str.
     * @return the number of bytes read including the newline
     * @throws IOException if the underlying stream throws
     */
    public int readLine(Text str, int maxLineLength) throws IOException {
        return readLine(str, maxLineLength, Integer.MAX_VALUE);
    }

    /**
     * Read from the InputStream into the given Text.
     *
     * @param str the object to store the given line
     * @return the number of bytes read including the newline
     * @throws IOException if the underlying stream throws
     */
    public int readLine(Text str) throws IOException {
        return readLine(str, Integer.MAX_VALUE, Integer.MAX_VALUE);
    }

}
